// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#ifndef DRACO_CORE_VARINT_DECODING_H_
#define DRACO_CORE_VARINT_DECODING_H_

#include <type_traits>

#include "draco/core/decoder_buffer.h"
#include "draco/core/symbol_coding_utils.h"

namespace draco {

// Decodes a specified integer as varint. Note that the IntTypeT must be the
// same as the one used in the corresponding EncodeVarint() call.
template <typename IntTypeT>
bool DecodeVarint(IntTypeT *out_val, DecoderBuffer *buffer) {
    if (std::is_unsigned<IntTypeT>::value) {
        // Coding of unsigned values.
        // 0-6 bit - data
        // 7 bit - next byte?
        uint8_t in;
        if (!buffer->Decode(&in))
            return false;
        if (in & (1 << 7)) {
            // Next byte is available, decode it first.
            if (!DecodeVarint<IntTypeT>(out_val, buffer))
                return false;
            // Append decoded info from this byte.
            *out_val <<= 7;
            *out_val |= in & ((1 << 7) - 1);
        } else {
            // Last byte reached
            *out_val = in;
        }
    } else {
        // IntTypeT is a signed value. Decode the symbol and convert to signed.
        typename std::make_unsigned<IntTypeT>::type symbol;
        if (!DecodeVarint(&symbol, buffer))
            return false;
        *out_val = ConvertSymbolToSignedInt(symbol);
    }
    return true;
}

}  // namespace draco

#endif  // DRACO_CORE_VARINT_DECODING_H_
